week 3: 10.5 muscle fibres produce different amount of tension depending on sarcomere length and frequency of stimualtion

Question 1

the amount of tension produced by an individual muscel fiber in a contraction depends on

Answer 1

the number of power strokes performed by cross- bridges

Question 2

why is a mucle fiber either all on (producing tension) or all off (relaxed)

Answer 2

calcium ions are released from all triads in the muscle fiber at the same time

Question 3

tension production is greatest when

Answer 3

a muscle is stimulated at its optimal length

Question 4

what does tension production depend on

Answer 4

fibers resting length at time of stimulation
which determines the amount of overlap between thick and thin filaments

Question 5

why does tension production depend on frequency of stimulation

Answer 5

frequency of stimulation affects the internal conc of calcium ions and therefore the amount bound to troponin

Question 6

length tension relationship

Answer 6

the amount of force a muscle can generate depends on the length at which it is held

Question 7

advantage of resting sarcomere being within its optimal range of lengths

Answer 7

maximum number of cross-bridges can form
therefore maximum amount of tension produced

Question 8

how does increasing the sarcomere length reduce tension produced

Answer 8

reduces the zone of overlap and therefore the number of potential cross-bridges

Question 9

how does a decrease in resting sarcomere length reduce efficiency

Answer 9

the stimulated sarcomere cannot shorten very much before the thin filaments extend across the centre of the sarcomere (M line) snd collide with thin filaments of the oppsoite side
interferes with AP propagation
number of cross-bridges reduced
tension declines

Question 10

twitch

Answer 10

single stimulus-contraction-relaxtion sequence in a muscle fiber

Question 11

latent period of a twitch

Answer 11

begins at stimualtion
lasts 2 msec
AP sweeps across sacrolemma
SR releases calcium ions

Question 12

contraction phase

Answer 12

tension increases to a peak
calcium ions binding to tropnin
active sites on thin filament being exposed
cross-bridge interactions occur
contraction phase end 15msec after stimualtion

Question 13

relaxation phase

Answer 13

lasts 25msec
calcium ion conc decreasing as calcium ions being pumped back into SR
active sites being covered by tropomyosin
number of active cross-bridges declining as they deattach
tension decreases to resting level

Question 14

what happens if a skeletal muscle fiber is stimulated directly after relaxation phase of twitch has ended

Answer 14

resulting contraction will develop a slightly higher maximum tension than the first contraction

Question 15

treppe pattern

Answer 15

the tension will increase with each stimulation over the first 30-50 stimulations if stimulated directly after relaxation period has ended

Question 16

explanation for treppe pattern

Answer 16

result from the gradual increase in concentration of calcium ions in the cytosol

Question 17

what muscles undergo treppe

Answer 17

cardiac muscles
most skeletal muscles do not

Question 18

wave summation

Answer 18

occurs when successive stimuli arrive before the relaxation phase has been completed

Question 19

incomplete tetanus stimulation

Answer 19

occurs if the stimulus frequency increases further
tension production rises to a peak and the periods of relaxation are very brief

Question 20

complete tetanus stimulation

Answer 20

stimulus frequency so high
that the relaxation phase is eliminated
tension plateaus at a maximum level